Bug 31876: Add an html validation test to Makefile

This shows we have 3 errors in main namespace and 2 in special
namespace. Both appear to be core issues which would be great to fix.

Made naming more consistent, moved comment in Makefile to a separate
line (jgonera)

Bug: 31876

Change-Id: I1414e2fbc71b090e07d4a1073ee3b6f3159f3759
Merge "Bug 31876: Add an html validation test to Makefile"